Air Compressors Buying Guide

We generally think of tools as being divided into two basic categories: Hand tools and power tools run by electricity. But there is an alternative to electric power tools. These are air tools, which are powered by compressed air, rather than directly from electricity.

In order to power air tools, you'll need an air compressor. An air compressor converts gas or electricity into power by compressing air into a tank. When the air is released, its expansion creates energy that can power nailers, wrenches, sanders, sprayers, and other types of power tools.

One of the advantages of running tools with compressed air is that the tools tend to last longer than electric power tools. They don't require the heavy motors that electric power tools do, so you don't need as much strength to lift them, and you won't tire so quickly when you do. Air tools don't generate heat the way that electric power tools do. They aren't associated with the hazards of fire or electrical shock. Air power can deliver a higher torque to the tool and a higher RPM--all of which helps you get the job done more quickly.

Inflators These small air compressors are used specifically for inflating tires, air mattresses, or inflatable items. They are excellent, convenient machines to have around the house--cutting down on the number of trips you might otherwise need to make to the gas station. If you get one with a cigarette lighter adapter, it will increase its convenience, since you can use it on car trips, as well as around the house and garage.

Cordless Inflators You can find cordless air compressors that are suitable inflating auto or bicycle tires, balls, and air mattresses. The main advantage to a cordless air compressor is the convenience of using it on the go. Since the battery doesn't have enough power to keep going for hours at a time, it's not suitable for powering air tools, such as finish nailers or impact wrenches.

Single Tank Compressors These air compressors, using a single air tank, are very portable. If you are moving from room to room, then you'll appreciate their relatively light weight (20-30 lbs). They are generally powerful enough for finish nailing. Some can even handle roofing or framing.

Pancake Compressors Pancake air compressors can be recognized by their distinctive round, flat tanks. These tanks hold more air than the single cylinder tanks. Consequently, these machines are more powerful--able to handle multiple tools. They tend to weigh from 35-60 lbs, so they are not quite as portable as single tank compressors.

Twin Stack Compressors If you have more than one or two carpenters working at the same time, a twin stack is a good choice. This is an air compressor with two twin horizontal cylinder tanks stacked one above the other. The capacity of a twin stack is comparable to the pancake air compressors, around 4 gallons between the two tanks. But these systems are heavier (over 60lbs) and more awkward to move. It's a good idea to get the feel of a twin stack if you do plan on moving it around, as some models are better balanced than others.

Vertical Compressors Vertical air compressors are not portable. These are large scale machines with tanks that hold from 15-80 gallons of air. However, they have a smaller footprint than other air compressors, making them a good choice for a stationary source of air power in a professional shop or garage.

Intermittent or Continuous Use
When you are looking for an air compressor, you need to consider how much power you need and how long you will need it for. A major consideration is whether you will be using your air compressor for continuous use or intermittent use.

Intermittent use means that you will be starting and stopping as you work with your tool. Continuous use means that you are powering a machine, like a sander, grinder, or sprayer, that stays on for minutes at a time. If you are planning to power an air tool continuously, you will need to an air compressor with a much larger air capacity than if you are using the tools intermittently.

The size of the air tank is an important factor in determining air capacity, although you can keep the compressor engine working to refill the tank even as you continue to use it.

Rotary screw compressors are better at providing a continuous flow of pressurized air than reciprocating compressors. The reciprocating compressors may be less expensive, though, and are fine for intermittent work.

Power Ratings
Cubic Feet per Minute (CFM) or the Standardized CFM (SCFM), combined with the Pounds per Square Inch (PSI) determine how powerful the air compressor is. The SCFM at a specific PSI (i.e. x CFM at 90 PSI) measures how much power you have available. A good rule of thumb is to check the rating for your air tool and multiple it by 1.5 to determine the minimum amount of CFM you'll need.

The CFM ratings are usually based on intermittent use. If you want to use the air compressor continuously, you'll need to increase the minimum CFM amount by at least 4 to get enough power for your usage.

Oil-Lubricated or Oilless Pumps
Another feature to consider is whether you want an oil-lubricated compressor pump, or an oilless system. In an oil-lubricated pump, a reservoir of oil helps maintain an airtight seal and lubricate the moving parts of the pump. This keeps the machine working longer without breaking down. But an oil-lubricated air compressor requires regular maintenance and there is a danger that it will spit oil onto the finished surface of your project.

Also, you have to make sure that your compressor remains level. Even a slight slant can keep the engine from lubricating properly and cause a breakdown. There are oil-lubricated air compressors that will shut down automatically if the oil level gets too low. This can save money on repairs.

An oil-less system will be much less work and worry. But it won't be able to run as long as the oil-lubricated systems. It will be quite a bit noisier. It will probably break down more easily, and require more repairs. But for very light use, it may be ideal.

Other Considerations
Check the noise level before you purchase any air compressor. These machines tend to be noisy, but some are quieter than others, and it will make a difference if you plan to use it for any length of time. Of course, you should always protect your hearing with ear plugs or ear muffs when working with power tools.

Be sure to check the power requirements before purchasing an air compressor. Most small or portable compressors only require the standard household 110-120 volt outlets. Larger compressors may require a 240 volt outlet. There are also gas-powered air compressors, which are the most convenient if you plan to use them on construction sites where electrical power can be hard to find.

The least expensive air compressors are going to be the very small inflators. These can cost as little as $10. The cordless versions are a bit more, starting at $25 and running up to about $150.

You can find a few more powerful air compressors for under $50, but you're going to find most of the systems, whether vertical, horizontal, or pancake, for prices between $100-300. These are air compressors most suited for home and small professional projects.

The large vertical air compressor machines (those that storage 30 or more gallons of compressed air) start at around $300. The largest systems (60-80 gallons) can cost in the mult-thousand dollar range.

Campbell Hausfeld
Chicago Pneumatic
DeWalt
Ingersoll Rand
Porter-Cable